|TRACKING DOWN THE ROOTS OF OUR SANITARY SEWERS|
EARLY SEWAGE CONVEYANCE SYSTEMS
Manholes: In the very early collection systems (especially for "separate" sanitary sewage systems), only lamp-holes were installed. It was soon learned that the lamp-holes were good for seeing (with a source of light) if the sewer in the main was indeed flowing, but they were almost useless as a maintenance access point. Consequently, the placement of manholes in gravity sewer systems soon became common (and essential).
Source: The Designing, Construction, and Maintenance of Sewerage Systems,
by H. Prescott Folwell, 1901.
The main purpose of manholes was (and is) to give admittance to the sewers for inspection and cleaning. To do so, it is imperative that they be big enough to allow people of average size to enter into them and to work.
A second purpose of manholes was to serve as points of ventilation for the gravity sewers. It was recognized early on that sewers need to "breathe," both in and out. Vented manhole covers could facilitate that need. Also, it was understood early that it was better to vent the system through the manhole covers than (as an alternative scenario) to vent the sewers through the plumbing systems of the connected homes. (Interior plumbing systems in those days didn't have water-filled traps to keep odors out of the rooms of the connected buildings.)
In the early larger sewers in Europe, the manholes were built off to the side of the sewer (proper) and connected to the sewer via an interconnecting underground passage. This approach was thought to be better for accessing the sewer and for avoiding having manhole rim/cover assemblies in the streets (proper). The drawback realized was that this approach was very expensive, and the passageway was a constant collector of filth/debris.
The size of the manhole opening was chosen early on to be 24" diameter -- the exact reason remains unknown -- with the diameter of the structure increasing to 4' to 5' at the sewer, thus allowing sufficient room for the sewer maintenance people to do their work. Early on, descent down into a manhole was made by use of a ladder or a rope; however, it soon became common to build steps into the manhole structure, sometimes via protruding bricks or stones, or wrought iron/cast-iron steps (wrought iron being better).
The walls of the early manholes were made of bricks mortared together (often with a coating of plastic on the outside). Soon concrete also came to be used for the construction of the risers.
The top of the manholes was "capped" with an iron casting (a.k.a. "rim and cover" or "frame and cover") deep enough (8" to 12") to permit the laying of brick or stone paving up to it. The early covers were made to contain as many ventilation holes as possible.
When the rim and cover assemblies (a.k.a. "manhole heads") of manholes were placed in unpaved areas, it was soon learned that a lot of sand/dirt would get into the sewer through the vent holes in the covers. Early on, a bucket was designed for suspension under the cover to catch the sand/dirt; it was sized smaller than the overall diameter of the casting assembly (nominally, 24" in diameter) so as to allow air to pass by the bucketthus allowing the sewer to continue to breathe.
Samples of Definitions of Terms Used in Sewerage and Sewage Disposal Practice
Source: Originally created in 1915 by the American Public Health Association. Later, The American Society of Civil Engineers worked with the APHA to finalize and publish these definitions in 1928.
Manholes covers: covers started off as slabs of stone, maybe pieces of wood -- which they remained from 3500 BC through the 1750s-1850s CE. For the last 200+ years, iron works in the United States have made cast-iron manhole covers, some weighing as much as 300 lbs. each, some rectangular, some square, but for the most part, round. The oldest available foundry catalog for manhole covers dates back to 1860.
The phrase "manhole" -- even though some people today want to change it for gender-sensitivity reasons -- was first used to describe the access holes between the decks of old, all-male, sailing ships. The word "manhole" (initially) had nothing to do with sewers.
It wasn't until later that the term was used to describe the structure through which access to sewers (initially, to new "separate" sewers) for maintenance could be achieved. Perhaps the name was adopted because it was, in essence, a hole into which a person (man) would go to do maintenance, or it was adopted from one level (street level) to another level (the sewer beneath the street). We'll probably never know for sure.
In fact, some believe the word "sewer" is derived from the term "seaward" in Old English. Early sewers in the London area were open ditches which led to the Thames River, and from there on down to the sea ("seaward").
As you can see, not a whole lot has changed in the years between the 1870s and now relative to the philosophy of manhole design, definitions, etc.; mainly materials and installation techniques have changed. The early designers had an amazingly good sense of what was needed.
Sewer pipe: In the very early years of sewers in the United States, hollowed-out logs were utilized to convey sewage from a single dwelling to the nearest stream or, sometimes, as a part of a larger conveyance "system" for a small town. Some larger "combined" systems utilized brick, sometimes cut stone, slate, or even wood (mostly, for the inverts); many combinations of materials were utilized depending on the types of materials available locally. The size/shapes of the sewers varied in almost direct proportion to the number of designers involved.
"Sewerage as a Beverage"
Source: Plate 7 of Sewers: Ancient & Modern, by Cyrenus Wheeler, Jr.
From the Collections of the Cayuga County Historical Society, 5 (1887).
In the early years, the joints of the sewer pipe were not sealed. It was thought then that allowing groundwater in through these joints would not only help drain the soil but would also "bring in" water to help convey the solids in the sewage on down through the sewer. No concern was felt (then) for the possibility of sewage leaking out into the ground water.
By the time the more systematic sewering of towns/communities became needed, the industrialization of the United States resulted in a much wider variety of pipe materials being available. The joints of these new pipe materials were still suspect, but via trial-and-error, ways to more effectively seal the joints came into being.
Sometime in the 1820s in Europe, the concept of building oval-shaped sewers evolved (as opposed to the previous flat-bottom, rectangular cross-sectional sewers), supposedly to help diminish the possibility of the sedimentation of solids/sand via the provision of higher (scour) velocities at low flows.
The smaller sewers built after the 1850s in the United States were generally made of vitrified clay or of cement mortar; brick was used for the larger-sized conduits. The older parts of New York City employed a lot of wood stave pipe for their sewers. Starting in Washington, D.C., concrete was used for large diameter mains; St. Louis, Kansas City, Detroit, and Philadelphia soon followed. Soon clay tiles were used to line the concrete pipe in order to minimize the impact of internal corrosion. Early sewer main installation procedures utilized trenches dug by hand. Bucket machines (steam driven) came into use via the Boston main drainage works project. Steam shovels came later.
Advertisement for Redwood (Stave) Pipe
Manufacturer: California Redwood Pipe Company (Los Angeles, CA).
Source: 1924 Classified Buyer's Guide of the City of Monrovia, CA.
For sewers to be made of brick, certain features had to be respected; more specifically:
As the pros/cons of brick sewers were understood, the impetus for other newer and longer-lasting pipe materials arose.
By the 1880s-1900s, vitrified clay pipe (with a salt glazing applied to both the pipe's interior and exterior surfacesa "carry-over" process from Europe) was the material of choice for a lot of the sewers up to 30" I.D. Cast iron also became available and was especially useful in "structural" situations.
The larger scale production of clay pipe in the United States was started
in 1849 by the firm of Hill, Merrill and Company in Middlesbury, Ohio
(not far from Akron). Their first product was hexagonal water pipe. Soon
they began making round clay sewer pipe. Early on, the bell & spigot
joints were added/formed manually onto the cylindrial shafts formed from
mechanical presses. During the next 20-25 years, the overall process became
almost fully mechanized. Clay pipe was very heavy by nature. Delivering
it required the availability of either rail or water transport. Until
those systems developed, clay pipe plants were created in many towns --
wherever there was a need and an adequate
supply of clay.
"Salt glazing" was accomplished by throwing salt into the kiln at the proper time; the vapors produced a vitreous coating as the exposed surface of the pipe. The Akron Sewer Pipe Company of Akron, Ohio, was the largest factory for glazed vitrified clay pipe in the 1890s in the U.S.; they employed the noted glazing process. The maker of salt-glazed pipe said it could only be made from clay that will vitrify -- that is one that will become hard and not porous when subjected to high heat.
"Slip glazing" was accomplished by dipping the unburnt pipe into a mixture of "slip clay" (a.k.a. "Albany earth") and water. This produced a glazing when the wetted pipe was subjected to high heat in the kiln. This process was utilized when the clays were of a type that would not vitrify, i.e., the pipe's surface remained open/porous.
A quote from Colonel George E. Waring (1880s):
The laying lengths were generally 2' long; in addition, in the early years, care had to be taken not to overload (structurally) or damage the pipe during its installation and/or backfill.
Pre-cast concrete pipe (not poured in place) began to be competitive in the early 1900s; however, it often weighed almost twice as much as the clay pipe and was almost always more expensive.
The joints of clay pipe were generally of the bell-and-spigot type, with the sealing material being cement mortar. Other materials for the seals were tried, such as the Stanford preparationa tar and sulphur combination. Asphalt was tried (with and without a mineral filter); sulphur and sand (a "rigid" combination), coal tar, and a mixture of pine tar and cement kneaded together were also tried -- but most favored cement mortar as a joint sealant (even for glazed clay pipe -- with which special care had to be taken to affect a good seal with the mortar). [One of the big worries early on was that if a lot of the sewage leaked out through poorly sealed joints, there wouldn't be enough sewage left in the main to provide decent cleansing velocities! On the other hand, if a lot of groundwater did "happen" to get into the sewer, that was okay because the velocity of sewage flow (in the pipe) would improve!!]
As the industry improved, and it was realized that fewer joints (especially if they weren't always well sealed) were better, the industry responded with 3' laying lengths of pipe.
"The Manufacture of Drain Pipe"
Source: The Manufacturer and Builder, April 1881, p. 82.
Cast-iron pipe began to become available in the mid-1700s for municipal water service. The first large-scale use of cast-iron pipe for distribution of water occurred in 1664 at Versaille, France. A 15-mile cast-iron main was installed from Marley-on-Seina to the palace at Versailles; the system is still in service today. The bell-and-spigot joint was developed by Sir Thomas Simpson in 1785 (London) for cast-iron pipe and has been in use ever since. The early versions used "butt" joints sealed with metal bands.
The first cast-iron pipe manufactured in the United States was produced
in a foundry in Weymouth, New Jersey, in the early 1800s. The city of
Philadelphia began installing cast-iron pipe in its water distribution
system (approximately 1804-1810) to replace some deteriorated old spruce
log wood pipe (reinforced at the ends with bands of wrought iron). In
fact, Philadelphia was the first American city to use cast-iron pipe exclusively
-- due to its greater longevity and the fact that water pressure that
could be maintained with it was higher than wood pipe could handle. For
years, the higher quality cast-iron pipe made was cast with a "P",
indicating that the pipe met the rigorous standards of Philadelphia's
By 1898, there were 71 foundries (in 17 states) in the United States making cast-iron pipe -- both pressure pipe and soil pipe (coated inside and out with coal tar). By the late 1800s, several foundries were devoted to making soil pipe, often used for plumbing systems within/under buildings. Cast-iron pipe began to be more widely used for sanitary sewers, especially in "structural" situations.
The proper ventilation of sewers began to receive more (and proper) attention,
although not as much as it should have received. The English custom of
disconnecting house sewers from street sewers (as opposed to the continental
custom of ventilating the latter through the former) is still the prevalent
one in our country. A change, however, began to take place, starting in
approximately 1890. The city of Newton, Mass., began ventilating its street
sewers through the house sewers with very beneficial results. A number
of other cities began to do the same, and, as a result, avoided much of
the odor sometimes rising from the manhole cover perforations. Much more
attention was now being given than before to details such as proper forming
of sewer junctions to prevent deposits, smoothness of the wetted perimeter
to prevent retention of solids, the hydraulic grade vs. invert grade when
proportioning for rain water capacity, and creating a straight mainline
alignment by which all sewers could be inspected throughout their length.
Progress was also being made in the use of better materials for construction.
The requirement for smoothness demanded the use of a better class of brick
and more truly formed pipes than were formerly utilized, and the use of
concrete for construction began to claim the advantage.